1. Field of the Invention
The present invention relates to a host terminal emulator that is software to make a common computer work as a terminal device for operating a host computer.
2. Prior Art
Conventionally, dealers who use general purpose computers, such as a main frame, as a business-use host computer were able to operate the host computer only through dedicated terminals connected with the host computer. However, more recently, since personal computers generally marketed have become powerful and communication environment has been improved, personal computers can be used as terminals. Therefore, it became unnecessary for dealers to own dedicated terminals.
In order to use a personal computer as a terminal, it is necessary to connect the personal computer with a host computer through a network, and to install a communication control program, which is used for transmitting/receiving data to/from the host computer, and software called a host terminal emulator on the personal computer. The personal computer on which the communication control program and the host terminal emulator are running is called a host terminal.
The host terminal transmits a command inputted by an operator to the host computer. The host computer that received the command performs process in response to the command, transmitting the screen data to the host terminal for updating some or all of contents on the screen to display the result of the process. The host terminal that received the screen data updates some or all of contents displayed on the screen based on the screen data. After finishing a series of updates of the screen, the host terminal stands by until the following command is inputted.
Incidentally, the screen displayed on a conventional host terminal is the simple screen constituted by many characters such as numerals, alphabetic characters, kana, Chinese characters and symbols, and many blanks, i.e., a CUI (Character User Interface) screen. However, a recent host terminal requires a GUI (Graphical User Interface) screen. That is, it is required that data of a CUI screen is displayed as a GUI screen that includes many GUI parts such as a text box.
In addition, the screen data for displaying a CUI screen on the host terminal (it is referred to as CUI screen data) sent from the host computer consists of records each of which includes coordinate value prepared for every coordinate in a text coordinate system defined by a line and the number of characters in a text-based screen, character codes, and attribute information. The attribute information shows the attribute such as a type of field (a protecting field or a non-protecting field), a position of a ruled line, a color of a field, a character type of field (an alphabetic character field, a kana field, a Chinese character field), an initial position of a cursor, etc. Since the CUI screen data was constituted in such a manner, the host terminal emulator could employ any one of two methods to generate the screen data for displaying a GUI screen (it is referred to as GUI screen data) based on CUI screen data.
The first method is to prepare the screen data of GUI screens corresponding to all kinds of the CUI screens, respectively. For example, see Japanese Patent Provisional-Publication No. H06-035855. According to the first method, the host terminal extracts the character string that specifies the kind of CUI screen from CUI screen data, reading the initial data of the GUI screen from a disk corresponding to the extracted character string. Then, the host terminal outputs the GUI screen data in which the other character strings in the CUI screen data are incorporated into the predetermined position in the initial data. According to the first method, the GUI parts can be freely arranged in the GUI screen independently of the attributes and arrangements of the characters in the CUI screen, which increases the visibility of the GUI screen.
The second method is to replace parts that can be GUI parts in a CUI screen by GUI parts one by one. In the second method, the host terminal extracts the coordinates at which the specific attribute was set from the coordinates in the CUI screen data, generating GUI screen data in which the GUI parts corresponding to the specific attribute are set at the extracted coordinates. According to the second method, the host terminal emulator can always generate GUI screen data based on CUI screen data, even if any kinds of CUI screen data are sent from the host computer.
However, according to the first method mentioned above, GUI screen data must be prepared for all kinds of CUI screens that could be outputted. For this reason, when there are the 2000 or more kinds, for example, the preparation of the GUI screen data, i.e., the development of the host terminal emulator, needs huge time and effort.
Moreover, according to the second method mentioned above, if one of the attributes that should make a pair like a non-protecting field attribute and a protecting field attribute does not exist in CUI screen data or it is set at a wrong coordinate, a GUI part may not be appropriately displayed on the GUI screen displayed on the host terminal. Therefore, such a GUI screen reduces visibility on the contrary.